A rail vehicle transportation system may include tracks over which rail vehicles travel. These tracks may cross routes of other transportation systems, such as road or highway systems over which automobile traffic may pass. To warn automobiles, crossing gates may be provided at locations where the tracks intersect roads, with the crossing gates configured to warn motorists and inhibit automobiles from crossing the tracks while a rail vehicle is traveling on the tracks at or near the crossing.
Some known railroad crossings use a warning predictor track circuit that detects motion of a train towards the crossing. Warning predictors may calculate the time of train arrival to the crossing based on the detected motion, and activate the crossing warning devices (lights, gates, bells, or the like) a specified minimum amount of time prior to train arrival at the crossing. The minimum amount of time may be set by a government regulation, or set to exceed a government regulation. Crossing predictors are commonly used where there are mixed train types (freight, passenger, or the like) and/or where train speeds vary dramatically.
In some systems, for example rail systems that use catenaries or third rails to provide energy to rail vehicles, electrical interference may be too high for predictor systems to function accurately. Thus, in some applications, crossing gates or lights may be activated based on train occupancy within a given distance of a crossing, without respect to relative speed or arrival time of a train at a crossing. If track circuits that simply activate the crossing based on train occupancy are used (as opposed to detecting train motion), the warning times provided at the crossing can vary significantly depending upon train speed. Long warning times are undesirable because of the unnecessary delay caused to motorists, and also because overly long warning times may tempt impatient motorists to drive around crossing gates and/or disregard audible or visible warnings if the motorists do not see any trains approaching after some period of time.
Traditional predictor track circuits are limited by practical considerations to a range extending a given distance from a crossing. Thus, rail vehicles may travel at a speed that exceeds that predictor track circuit's ability to detect the rail vehicle's presence in time to lower a gate within a desired time range. Some systems account for such speeds exceeding the predictor track circuit's ability by sending a message from the rail vehicle when traveling at such higher speeds before encountering the effective range of the predictor track circuit, with the message conveying a relative time (from the time the message was sent) when the rail vehicle is expected to arrive at the crossing. Delays in sending, receiving, and/or processing the message with the relative time require that the crossing be designed to close at a time exceeding a desired time for closing, in order to account for worst case delays, which may be around ten seconds or more. In such systems, crossings will frequently activate earlier than desired, resulting in overly long waiting periods, and resulting in inconsistent wait times for motorists. Such systems also fail to address issues resulting from relatively slower speeds.